In vitro, in vivo and in silico anticancer activity and toxicity of Usnic acid extracted from the mycobiont culture of Usnea baileyi

Lichen has widespread uses in indigenous medicinal traditions, and it has been used to treat various conditions. Among the various active compounds in the lichen, Usnic acid has unique biological activities. However, the toxicology and the mechanism of action of Usnic acid need to be examined in detail to the extent of clinical trials. Hence, the present research is aimed to isolate usnic acid from the mycobiont culture of Usnea baileyi lichen and explore its toxicological properties and those of pharmacological importance. The methanolic extract of these mycobiont cultures has shown the presence of Usnic acid via column chromatography. The Usnic acid was computationally evaluated using molecular docking studies (GLIDE docking) and MMGBSA energy calculations. The results obtained from TLC, LC-MS, UV-VIS spectrophotometer, NMR spectroscopy (1H and 13c), and FT-IR indicated the presence of Usnic acid. An acute toxicity analysis by an in vivo study using a zebrafish animal model showed acute toxicity. The standard disc diffusion and DPPH assay suggested an antimicrobial and antioxidant activity with this lichen compound. The in vitro analysis of Usnic acid in G361 skin cancer cell lines demonstrated its anticancer potential against malignant melanoma. Furthermore, a molecular in silico study returned a good docking score of -7.977, and the MMGBSA free energy was measured as -18 and -30. Therefore, further extensive research on Usnic acid might lead to the development of novel anticancer drugs from the natural sources.